The dryer is rotating around the horizontal axis (z-axis) and contains a lots of spoilers that is close to the outer wall. There are water and vapor inside the dryer and VOF model is used. The gravity should be considered.

I have used MRF and aligned the gravity with -y axis (by opening the operation condition). But the result is not true. (the water anywhere seems to be attracted by the force that is -y direction)

I think the gravity item in N-S equation at rotating frame should be varied with time, while FLUENT assumes that it is constant. So it will be resolved by UDF.
Could you be agree with me?
Any views you can put?
I would be appreciated .